direct connect AS_Path prepending

Question

Dear Team - Trying to understand AS_Path Prepending for both the connection in non-VPC region. As per **https://repost.aws/knowledge-center/direct-connect-active-passive-connection, **

> Note: AS Path prepending can't be used to configure Active/Passive connections in the following scenarios: Connection A (virtual interface VIF-A) is in Region 1. Connection B (virtual interface VIF-B) is in Region 2. Both virtual interfaces connect to a VPC in Region 1 using a Direct Connect gateway.

However, what if both the VIF are in diff region than VPC ? Please refer below high level diagram along with AS PATH prepending. As per the my understanding, irrespective of AWS source region, traffic from AWS will prefer below order.

Transit VIF-1, Transit VIF-2, Transit VIF-3, Transit VIF-4

Is this correct understanding ?

![Enter image description here](/media/postImages/original/IMzOA0oh6zTq-SGknvPULHdg)

Answer

Hello,
As per documentation "AS_PATH prepending doesn’t work when the Direct Connect connections are in different associated AWS Regions than the VPC" : thus depending from which region your traffic is coming, the order described might no be exact.

https://docs.aws.amazon.com/directconnect/latest/UserGuide/routing-and-bgp.html#private-routing-policies

direct connect AS_Path prepending

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